Help!! Black on scales?!

[stewnew]

Hi everyone.
When trying to get some pictures of my tank today i noticed something alarmingly wrong with one of my malawi peacocks... It almost looks like black paint is on his scales...I saw something similar on another one of my fish in the same tank a while back.. but it went away and was never this bad...

Any Ideas? Also, any clue on an ID?

Sorry about the photo quality i used my phone : /

 

[stewnew]

He has a little black on his body naturally, but in the second two pictures you can see what I'm talking about, just behind his gills

 

[poly-nomial]

Maybe ammonia burn? Check your ammonia levels

 

[stewnew]

OK guys new problems evolving!
My sulfur head is showing some worrying symptoms now too. He doesnt have this same blackish issue with his fins, but his eyes are a little cloudy, and his fins (which are a bit chewed up from the other tankmates) are showing this strange grey-ish color...is this fin rot?
Does the fact that I am having both these issues have to do with my water quality? and if so what can i do about it?

 

[stewnew]

bump bump
please help me out i know someone out there has a clue about whatsup with my tank

 

[stewnew]

did the water test two days ago, then a 25% water change, and then tested again and got the same exact readings
pH 7.6-7.8 (was hard to tell exactly, an I used a pH range test as well as a high pH range)
Ammonia: 0 ppm
Nitrates: 0ppm
Nitrite: 0 ppm

so water is not the problem?